BRPI0710116A2 - process and apparatus for the production of three-dimensional ceramic bodies - Google Patents

Abstract

A process for producing three-dimensional shaped ceramic bodies by layerwise printing of a suspension comprising the constituents required for formation of the shaped ceramic bodies by means of an inkjet printer in the desired two-dimensional shape onto a support material, drying and hardening of the layer composite formed, which is characterized in that printing is effected using a suspension comprising from 50 to 80% by weight of ceramic particles in a dispersion medium comprising an aqueous boehmite sol, at least one low molecular weight alcohol, at least one drying inhibitor and at least one organic fluidizer, and also an apparatus for carrying out this process are described.

Description

"PROCESS AND APPARATUS FOR THE PRODUCTION OF CERAMIC BODIES

THREE DIMENSIONALS "

description

The present invention relates to a process for producing three-dimensional ceramic bodies by printing on layers of a suspension comprising the constituents required for the formation of the ceramic bodies formatted by means of an inkjet printer in the desired two-dimensional format on a support material, drying and hardening of the formed composite layer and also to an apparatus for carrying out this process.

Conventional processes for the production of three-dimensional ceramic bodies generally comprise the use of tools such as pressing or casting molds to match the formatted bodies to be produced. Although this method is suitable for producing a large number of three-dimensional bodies, the process is disadvantageous when only numbers Small bodies of formatted bodies with different three-dimensional shapes should be produced. This makes the production of prostheses for human bodies based on such three-dimensional ceramic bodies difficult because these prostheses must be individually adapted.

On the other hand, deformatting methods are also known which comprise direct construction and complex formed bodies from geometrically small units by controlled deposition of material, performed with computer controlled procedures from a three dimensional computer model. The important advantage compared to conventional formatting methods is freedom of formatting, with supportive constructs also being able to be employed if appropriate. Computer controlled production processes of this type are also called free solid form manufacturing or rapid prototyping. While the latter encompasses micro-extrusion, stereolithography, laser generation and the like, selective laser sintering and inkjet printing has also become known for the production of free-forming solid bodies (SFF).

Thus EP 0 847 314 B1 describes a process for producing a sintered substrate structure in which a particulate-laden liquid is applied by means of a substrate inkjet printer, after which the liquid is evaporated and the remaining particles are sintered. In this process, particleinterintering is performed in layers by laser means. This method is unsatisfactory in that the need for layer sintering of particles by means of a laser makes the use of complicated apparatus necessary.

In J. Am. Ceram. Soc., 85 (2002), 2113-2115, X. Zhaoet al. describe the production of vertical ceramic walls by layered printing of a printing liquid containing ceramic particles by means of an inkjet printer. The printing liquid used herein comprises zirconium dioxide particles, a dispersant, isopropyl alcohol, octane and wax. After the printing of the individual layered liquid through the inkjet printer, with the printing table being lowered in the ζ direction each time, the three-dimensional objects are dried and then pyrolyzed at elevated temperature to remove the organic constituents. ZrO2 ceramic particles are subsequently sintered.

However, it has been observed that this process is not suitable for mass production of three-dimensional ceramic bodies because the used printing liquid does not have the required stability, with the settling of the suspended ceramic particles, blocking the nozzles of the inkjet printer head and, ultimately not allowing uniform adherence of the ceramic material in the desired layered form and thus the formation of the three-dimensional corpot. As a result, the bodies formed after pyrolysis and sintering do not have the desired dimensional accuracy and uniform density and thus strength.

It is an object of the present invention to provide a process and apparatus in which these disadvantages can be overcome and which make it possible to simply produce three-dimensional multi-shape ceramic bodies with high dimensional accuracy and constant mechanical properties while solving the problem of stability and state. dispersion and the suitability of printing containing suspended ceramic particles for use in an inkjet printer.

It has been surprisingly found that this object can be achieved by the suspension used for printing by means of an inkjet printer comprising a dispersion medium containing suspended ceramic particles, with the dispersion medium comprising a bohemian soluble as an essential constituent.

Accordingly, the invention provides the process as claimed in claim 1 and the apparatus as claimed in claim 39.

The dependent claims relate to preferred embodiments of these objects of the invention,

Thus, the invention provides, in particular, a process for producing three-dimensional ceramic bodies by layering a suspension comprising the constituents required for forming the ceramic bodies formatted by means of a desired three-dimensional inkjet printer on a support material, Drying and hardening of the layered composite formed, which is characterized in that the printing is effected using a suspension comprising from 50 to 80% by weight of ceramic particles in a dispersion medium comprising a deboemite aqueous sol, at least one low molecular weight alcohol At least one drying inhibitor and at least one organic fluidizer.

It has been surprisingly observed that the suspension used as a printing liquid in the process of the invention shows very good stability and even very high desolate content virtually shows no sedimentation tendency of the ceramic particles. If necessary, the ceramic particles can be dispersed by simple agitation. In addition, the suspension used according to the invention has a suitable viscosity for the present process and good wetting and drying behavior even with high solid contents, namely a ceramic particle content of 50 to 80% by weight. In contrast to the known prior art teachings, it is possible by this suspension and process of the invention to produce any three dimensional ceramic bodies having high precision and uniform mechanical properties without the formation of voids in the sintered formatted ceramic bodies.

In a preferred embodiment, the bohemite solids content present in the dispersion medium of the printing suspension according to the invention is from 0.001 to 2% by weight, more preferably from 0.001 to 1% by weight and even more preferably from 0.01%. 0.5% by weight. Here, the Bohemite weld contains nanocrystalline Bohemite particles dissolved in aluminum hydrate.

The nanocrystalline boehmite particles (AlO (OH)) preferably have a particle size of from 3 to 20 nm, more preferably from 4 to 5 nm, and advantageously in particular have a length to aspect ratio of 1.4. : 1 to 2.2: 1, as a result of which ceramic particles can be kept in suspension in a particularly stable manner.

As a dissolved aluminum hydrate, the bohemian sun present in the dispersion medium according to the invention comprises the neutral or ionic compounds of the following [Al (H2O) 6] 3+, [Al (H2O) 5OH] 2+, [Al (H2O ) 4 (OH) 2] +, Al (OH) 3 (aq), [Al (OH) 4] ".

According to the invention, it is particularly advantageous that the bohemian sun has a pH of from 1.7 to 11, preferably from 4 to 10 and even more preferably from 5 to 8. At a pH of the bohemian sun in this range, colloidal suspensions may be maintained. very good stability of the ceramic particles while at the same time obtaining good pumping capacity and good printability of the suspension.

In a preferred embodiment of the invention, the dispersing medium comprises 48 to 88% by weight of the bohemian sun, 50 to 20% by weight of low molecular weight alcohol, 50 to 20% by weight of drying inhibitor and 2 to 12% by weight of organic fluidizer or organic dispersant.

The dispersion medium preferably comprises ethanol, ethanol, propanol, isopropanol or mixtures thereof as low molecular weight alcohol and a polyhydric alcohol, a long chain hydrocarbon or mixtures thereof, for example glycerol and / or ethylene glycol, as a drying inhibitor. As an organic fluidizer or organic dispersant, the dispersion medium preferably contains a synthetic organic electrolyte preparation and / or a synthetic carboxylic acid. As an organic synthetic polyelectrolyte, preference is given to polyacrylic acid and / or polymethacrylic acid having an average molecular weight of 4000 to 6000, with these acids preferably present as a metal alkali salt or ammonium salt. These preferred organosynthetic polyelectrolytes produce a non-foamy suspension and, due to the presence of these organic fluidizers, can be readily applied in layers to a substrate material by means of a conventional inkjet printer. Particular preference is given to polyacrylic acids in the form of ammonium salts which may be from Zschimmer & Schwarz under the names Dolapix CE64, Dolapix PC75 and Dolapix ET85.

In a further preferred embodiment, the dispersing medium comprises from 62 to 91% by weight of the bohemian sun, from 5 to 10% by weight of ethanol, from 2 to 15% by weight of glycerol and / or ethylene glycol and from 2 to 8%. by weight polyacrylic acid and / or polymethacrylic acid in the form of the deammonium salt.

In an advantageous embodiment of the invention, the suspension used as a printing liquid comprises ceramic particles comprising pure Al2O3, pure ZrO2, pure Al2O3-ZrO2, pure Si3N4, bohemite stabilized Al2O3, ZrO2 stabilized with Y2O3, HfO2, CeO2, MgO, and / or Ca2 -ZrO2 stabilized with Y2O3, HfO2, CeO2, MgO and / or CaO, Si3N4 stabilized with Al2O3, Y2O3, Fe2O3 and / or rare earth oxides, or mixtures thereof.

The mixed Al2O3-ZrO2 ceramics which can be stabilized with Y2O3, HfO2, CeO2, MgO and / or CaO preferably comprise 30 to 70 wt% Al2O3 and correspondingly 70 to 30 wt% ZrO2. Preference is given to a Y2O3 stabilized ZrO2 which can be obtained from Tosoh, Tokyo, under the name TZ-3YS-E.

In accordance with the invention, particular preference is given to the suspension containing from 60 to 70% by weight ceramic particles. Here, the particle size of the ceramic particles should be smaller than the nozzle opening of the used inkjet printer head and feed lines, and is preferably in the d90 region of 0.01 to 3 µm, more preferably 0.5 to 0.5 µm. 1.5 μπι.

It is advantageous that the suspension of the ceramic particles in the dispersion medium according to the invention has a pH of 4 to 11, preferably 7 to 9, and a viscosity measured at 25 ° C and shear rates of γ> 400 of 5 to 25. mPas and a viscosity measured at low shear rates of γ <50 from 100 to 500 mPas, since the suspension can easily be transported and ejected by conventional inkjet printer pumps through the printheads and nozzles of these printers. the conventional ink jet.

In the process of the invention, the layers forming three-dimensional ceramic bodies are printed on a flat support material, for example, a graphite plate, a platinum sheet, a ceramic or a glass ceramic having a porosity of 0 to 10%.

In a further embodiment of the invention, it is possible to print the layers forming the three-dimensional ceramic body onto a support material on which one or more layers having definite dimensions and can be removed during hardening of the layered composite have been previously printed using. A suspension comprising a material which vaporizes during the hardening of the layered composite in the dispersion medium indicated. This makes it possible to form a three-dimensional ceramic body having recesses, specific similar openings, whereby it can be adjusted and joined to a corresponding counterpart, for example, the metal part or even a ceramic part of a dental implant in which the three-dimensional body is produced. according to the invention serves as a dental crown.

In a preferred embodiment of the invention, one or more layers having defined dimensions and may be removed during hardening of the composite into printed layers in addition to or between the layers printed through the first print head by means of a second print head using a suspension comprising a material. which vaporizes during the hardening of the layered composite in the indicated dispersion medium. This makes it possible for the three-dimensional ceramic body which has recesses, cuts, etc., in the desired locations, so that it can, with the aid of these, be adjusted to the counterpart to be joined, to be produced in a single printing step.

As a spray material in this embodiment of the invention, preference is given to the use of a material which vaporizes at a temperature above 200 ° C or pyrolizene in the presence of oxygen at a temperature above 400 ° C.

Even if the suspension or printing liquid used in the process of the invention shows a very low tendency of the ceramic particles to settle or to adhere to the printhead nozzles of the inkjet printer, the printhead nozzles are, in a preferred embodiment of the invention, clean by means of a cleaning liquid comprising water, a low molecular weight alcohol and / or a polyhydric alcohol after printing one or more layers. The cleaning liquid preferably comprises a mixture of water, ethanol and at least one polyhydric alcohol in a weight ratio of water: ethanol: polyhydric alcohol 6-10: 1-4: 1-3, preferably 8: 1: 1.

The cleaning of the print head nozzles is advantageously carried out in such a way that the cleaning liquid penetrates the nozzles and nozzle chambers. This cleaning liquid penetration into the nozzles and nozzle chambers can be effected by high external depression or sub-atmospheric pressure. The print cartridge containing the suspension. This can be achieved for example by the internal pressure of the gaseous phase print cartridges being adjusted to a value which is below 2 to 100 mbar (corresponding to 200 to 10000Pa), preferably below 2 to 25 mbar (corresponding to 200 to 100 mbar). Atmospheric pressure and which is in a particularly preferred variant controlled according to whether the suspension in the print cartridge is filled, such that the pressure difference inside the print cartridge remains constant as a function of the filling in the print cartridge. suspension in the print cartridge.

In a further preferred embodiment of the invention, printhead nozzle cleaning is performed by means of a body that is impregnated with the cleaning liquid and is periodically passed over the nozzle cleaning head at a contact pressure of 0.01 to 1N / mm2, preferably from 0.02 to 0.05 N / mm2. This body is preferably an open pore foam or a microfiber cloth or even a combination thereof, that is, for example, a left over pore foam which is stretched with a microfiber cloth. This body is, for example, cylindrical in shape and is pressed as it is rotated around its longitudinal axis at the contact pressure indicated against the printhead nozzles and beyond. In a preferred embodiment, the print head is moved beyond the cleaning device to its final position or any desired position.

In addition, ultrasonic cleaning of the nozzle heads can be performed, and this can be combined with mechanical cleaning using the body impregnated with the cleaning liquid. Cleaning of the print head nozzles is preferably performed periodically under ultrasound between pressure cycles in the print cartridge or the print head.

After printing, the printed layers are dried at a temperature of 65 ° C to 1052 ° C, with each individual layer preferably drying after application. This is preferably performed on each individual printed layer being dried in the printing region of the jet printer detected by heating to a temperature in the range of 65 ° C to 105 ° C, preferably from 682 ° C to 852 ° C, if appropriate using a blower with application of reduced pressure or convection flow to remove doliquid vapor. The drying of these layers may also be effected by irradiation with a halogen lamp, an infrared lamp, by ionic radiation, laser radiation or by using heating elements arranged in the printing region.

The impression of the suspensions is conducted such that the individual layers of the ceramic material after drying have a thickness of 1 µm to 30 µm, preferably 0.05 µm to 10 µm, and any individual layers of material that vaporizes during the hardening of the ceramic. composite layer on which they are printed have a thickness of 0,05 μτη at 5 | ± m.

After drying of the last layer, the dry layered composite obtained in this way is hardened by sintering the ceramic material, preferably for storage of the layered composite obtained after printing, if appropriate, at a high temperature in a drying oven, e.g. at a temperature of about 80 ° C. Curing of the resulting layered composite of the ceramic material to form the three-dimensional ceramic body is preferably effected by sintering at a temperature of 800 ° C to 1500 ° C. The sintering is preferably conducted at a sintered density of 100% of the theoretical density, preferably up to 98% of this density.

It has been determined that the use of the inventive process makes it possible to produce, with high dimensional accuracy, three-dimensional ceramic bodies that do not show any drying crack, show no separation of the individual layers and are exceptionally suitable for the production of medical prostheses.

The process of the invention is thus directed in particular to the production of ceramic medical prostheses, in particular prostheses in the body region, head, face, oral cavity, dental implants, dental fillings, dental crowns and dental bridges. The invention further provides an apparatus for carrying out the process, which is characterized by a conventional computer controlled inkjet printer containing a support for the support material, which can be moved vertically in the z-direction, can be lowered by a layer height a each time under the control of the computer and may be moved in the y direction, if appropriate, in the χ direction (the direction of the print head movement), a drying device in the print region, and a cleaning system for the print head nozzles.

The inkjet printer is preferably a commercial drop-on-demand printer that can be obtained, for example, Hewlett Packard Company, which has been modified by the installation of a print region drying device and a nozzle cleaning system. Print Head. The apparatus cleaning system preferably comprises a body that may be impregnated with the cleaning liquid and may be contacted with the printhead nozzles under pressure on the cleaning stage. The body that can be impregnated with cleaning liquid preferably is in the shape of an open pore foam umbilical over which the printhead nozzles are pressed under cleaning contact during the cleaning step. preferably be rotated around its longitudinal axis and dip into the cleaning liquid on its side against the print head. It is advantageous here that the axis of the foam cylinder is parallel to the printing direction of the jet printer, that is, the direction of the print head offset (x-direction) or perpendicular to it (y-direction).

In a preferred embodiment of the apparatus of the invention, a cleaning drum is provided to remove excess cleaning liquid between the point at which the foam cylinder exits the cleaning liquid and the point at which it contacts the print head of the printer. jet detinta.

In addition, the cleaning apparatus of the invention apparatus may comprise an ultrasonic bath containing cleaning liquid in which the printhead nozzles may be lowered. The ultrasonic bath of this embodiment is preferably located in the parking head region of the print head.

When the process of the invention is carried out in practice, the precise shape of the three-dimensional ceramic body to be produced is first generated on a computer, for example by scanning a model. For example, data required for the formatted body to be formed may be entered into a commercial computer through software such as Microsoft WORD. The dimensions χ and y of the future three-dimensional body are given by the two-dimensional representation of the object set forth in this document in the form of individual layers to be printed. The dimensionality of the formatted body is produced by the repeated printing of the individual layers having the appropriate dimensions.

The print cartridges are subsequently filled with the suspension to be printed, after which the print head is moved in accordance with the control program on the carrier material and the suspension is printed in the desired format as a layer. This layer is subsequently dried before applying the next layer. These measurements are maintained while at the same time the support of the support material is lowered one layer height at a time until the fresh three-dimensional ceramic body has been produced. This shaped body is subsequently, if appropriate, after storage at 80 ° C in the drying form, sintered at the temperature required for complete sintering of the ceramic material and produces the desired three-dimensional ceramic body with high surface accuracy and high surface quality.

This mode of operation according to the invention makes it possible to easily print over 10,000 printing cycles, i.e. over 10,000 layers having the desired two-dimensional format without the printer nozzles becoming blocked.

The following examples serve to illustrate the invention.

EXAMPLE

To produce the bohemite sol used in the dispersion according to the invention, 700 ml of water are raised to pH 2 by the addition of 65% potent nitric acid. The mixture is heated to 80 ° C and 2.1 g of bohemite (Dispersai P2 from Sasol, Hamburg) is added and the mixture is stirred for 10 minutes. The mixture is allowed to cool to room temperature, 25% potassium ammonia is added to a pH of 8.5 and the obtained bohemite aqueous sol is stored in a polyethylene flask.

In order to produce the actual impression dispersion, 150 g of the bohemian sun produced as described above are mixed with 30 g of 85% potent glycerol, 4.5 g of an ammonium polyacrylate (Dolapix CE64, daZschimmer & Schwarz, Lahnstein ) and 11 g of an ammonium polyacrylate (Dolapix PC75 from Zschimmer & Schwarz, Lahnstein) are added and the mixture is stirred for 30 seconds. Subsequently 450 g of Yttrium Oxide Stabilized Zirconium Dioxide (TZ-3YS-E from Tosoh, Tokyo) are added and the mixture is mixed in a dispersion apparatus (Ultra-Turrax T25 Basic, IKA-Werke, Staufen) on the head. of appropriate dispersion (S2 5N-10G, IKA-Werke, Staufen) at 6500 to 13500 min-1 per minute, with 25 g of ethanol being added during mixing. The mixture is subsequently dispersed at 24000 min-1 for a further 2 minutes and the suspension obtained is introduced into an empty printer cartridge.

In order to produce a suspension for the impression of layers which are removed during the hardening of the layered composite, 85 g of distilled water are added into a 250 ml polyethylene bottle and 8.5 g of glycerol and 2.5 g of polyacrylate. deamonium (Dolapix ET85, Zschimmer & Schwarz, Lahnstein). Then 1.5 g of polyethylene glycol 400, 34 g of ethanol and 38.5 g of carbon black (Arosperse 15, Degussa, Frankfurt) are added. 200-250 g of Al2 O3 milling medium having a diameter of 5 mm are added and the material is homogenized in drums for 40-45 hours. The grinding media is then removed and the suspension obtained is introduced into an empty printer cartridge.

A three-dimensional body forming the precisely sized recess in the three-dimensional ceramic body which ultimately must be produced is first printed on a support material comprising a graphite plate using the second suspension mentioned above. This is conducted using a drop-on-demand inkjet printer, which has been modified to make it possible for the computer-controlled lowering of the printing table in the direction to achieve a ceramic body layer construction. Three-dimensional. The print cartridges containing the indicated print suspensions are installed and the inkjet printer is operated in the usual manner, with the print head being moved in the usual manner under computer control in the χ direction on the support material that is moved in the y direction. printer. Positioning accuracy in this second operating mode is 20 μπι.

Each applied layer is subsequently dried by means of a halogen lamp, whose light is focused on the printing region by means of convex optical lenses. At the same time, a fan on the substrate produces convection and thus accelerates drying. During this procedure, the temperature of the support material and the applied layers are kept below 130 ° C, preferably about 80 ° C. After construction of the three-dimensional body of the vaporizing material during the layering of the composite composite, the printer cartridge is replaced by a printer cartridge containing the first suspension containing the ceramic particles of zirconium dioxide stabilized and a second three-dimensional body based on the ceramic particles. presenting the desired shape is layered in the same way over the first three-dimensional color, with the layers each being dried as indicated.

After manufacture of the three-dimensional body, it is briefly dried at a temperature of about 80 ° C in a drying oven and then heated to a temperature of about 400 ° C in the presence of oxygen to vaporize or pyrolyze the still-present organic components. The resulting three-dimensional body having the recess corresponding to the first three-dimensional body based on the vaporizing material during hardening of the layered composite is then sintered to a temperature of 1400-C to form the three-dimensional ceramic body having high dimensional accuracy and high surface quality.

This shaped ceramic body has a density of about 98% of the theoretical sintered density, no cracking, high flexural strength and is therefore highly suitable as a medical ceramic prosthesis, for example as a dental or implanted crown.

Claims (38)

1. Process for the production of three-dimensional ceramic bodies by layering a suspension comprising the constituents required for forming ceramic bodies formed by a desired three-dimensional inkjet printer on a support, drying and hardening material of the composite in a layer; characterized in that the printing is carried out using a suspension comprising from 50 to 80% by weight of ceramic particles in a dispersion medium comprising bohemian aqueous sol, at least one low molecular weight alcohol, at least one drying inhibitor and at least one organic fluidizer . Process according to Claim 1, characterized in that the bohemian sun has a solids content of from 0.0001 to 2% by weight, preferably from 0.001 to 1% by weight, more preferably from 0.01 to 0.5%. by weight Process according to claim 1 or 2, characterized in that the bohemian sun comprises nanocrystalline particles of bohemite and dissolved aluminum hydrate. Process according to any one of claims 1 to 3, characterized in that the bohemite nanocrystalline particles have a particle size of 3 to 20 nm, preferably 4 to 5 nm. Process according to any one of Claims 1 to 4, characterized in that the nanocrystalline boehmite particles have a length to width ratio of 1.4: 1 to 2.2: 1. Process according to any one of Claims 1 to 5, characterized in that the deboemite sun contains [Al (H2O) 6] 3+, [Al (H2O) 5OH] 2+, [Al (H2O) 4 (OH) 2] +, Al (OH) 3 (aq), [Al (OH) 4] "and / or Al3 ions as dissolved aluminum hydrate. Process according to any one of Claims 1 to 6, characterized in that the deboemite sun has a pH of 1.7 to 11. Process according to at least one of the preceding claims, characterized in that the dispersion medium comprises from 48 to 88% by weight of the Sunemite sun, from 5 to 20% by weight of low-molecular-weight alcohol, from 5 to 20% by weight. weight of drying inhibitors and from 2 to 12% by weight of organic fluidizers. Process according to claim 8, characterized in that the dispersion medium contains methanol, ethanol, propanol, isopropanol or mixtures thereof as low molecular weight alcohol, a polyhydric alcohol, a long chain hydrocarbon or mixtures thereof as a drying inhibitor and a synthetic organic polyelectrolyte and / or a carboxylic acid preparation as an organic fluidizer. Process according to Claim 9, characterized in that the dispersion medium contains glycerol and / or ethylene glycol as polyhydric alcohol. Process according to Claim 9, characterized in that the dispersion medium contains polyacrylic acid and / or polymethacrylic acid having an average molecular weight of 4000 to 6000, preferably in the form of an alkali metal salt or ammonium salt, with synthetic organic polyelectrolyte. Process according to any one of Claims 1 to 11, characterized in that the dispersing medium comprises 62 to 91% by weight of the deboemite sun, 5 to 15% by weight of ethanol, 2 to 15% by weight of glycerol. and / or ethylene glycol and from 2 to 8% by weight organic defluidizers. Process according to at least one of the preceding claims, characterized in that the ceramic particles comprise pure Al2O3, pure ZrO2, pure Al2O3-ZrO2, pure Si3N4, bohemite stabilized Al2O3, Y2O3 stabilized ZrO2, HfO2, CeO2, MgO and / or CaO, Al2O3-ZrO2 stabilized with Y2O3, HfO2, CeO2, MgO and / or CaO, Si3N4 stabilized with additional Al2O3, Y2O3, Fe2O3 and / or earth oxides, or mixtures thereof. Process according to Claim 13, characterized in that the mixed Al2O3-ZrO2 ceramic which can be stabilized with Y2O3, HfO2, CeO2, MgO and / or CaO comprises 30 to 70% by weight of Al2O3 and correspondingly to 70 to 30 wt% ZrO 2. Process according to any one of claims 1 to 14, characterized in that the ceramic particles are present in an amount of from -60 to 70% by weight in the suspension. Process according to any one of Claims 1 to 15, characterized in that the particle size of the ceramic particles is smaller than the aperture of the print head nozzles and the feed lines and is in the region of a d90 of 0.01 to 3. μm. Process according to at least one of the preceding claims, characterized in that the suspension has a pH of 4 to 11, preferably 7 to 9, and a viscosity at 25 ° C of 5 to 25 mPas at shear rates of γ> 400 and 100 to 500 mPas at low decay rates of γ <50. Process according to at least one of the preceding claims, characterized in that the layers are printed on a flat support material. Process according to Claim 18, characterized in that the layers are printed on a graphite plate, a platinum sheet, a ceramic or a glass ceramic having an open porosity of 0 to 10% as a support material. Method according to at least one of the preceding claims, characterized in that the layers are printed on a support material on which one or more layers having defined dimensions and which can be removed during the curing of the layered composite have been previously printed using a suspension. comprising a material which vaporizes during the hardening of the layered composite named dispersion name. Process according to at least one of the preceding claims, characterized in that one or more layers having defined dimensions and can be removed during hardening of the layered composite are printed between or in addition to the layers printed by the first half-print head. a second printhead utilizing a suspension comprising a material which vaporizes during the hardening of the layered composite in the indicated dispersion medium. Process according to Claim 20 or 21, characterized in that a material which vaporizes at a temperature above 2000 ° C or pyrolizes in the presence of oxygen at a temperature above 400 ° C is used as a material which vaporizes during hardening of the composite layer. . Process according to at least one of the preceding claims, characterized in that the printhead nozzles are cleaned by means of a cleaning liquid comprising water, a low molecular weight alcohol and a polyhydric alcohol after printing one or more layers. Process according to Claim 23, characterized in that a mixture of water, ethanol and at least one polyhydric alcohol is used in a proportion by weight of water: ethanol: polyhydric alcohol of (6-10): (1-4) : (1-3), preferably 8: 1: 1, as cleansing liquid. Method according to at least one of the preceding claims, characterized in that the nozzle cleaning of the print head is conducted in such a way that the cleaning liquid penetrates the nozzles and the nozzle chambers. Process according to Claim 25, characterized in that the liquid penetration of the nozzle cleaners and nozzle antechamber is carried out by increasing external pressure or sub-atmospheric pressure in the pressure cartridge containing the suspension. Process according to Claim 26, characterized in that the cleaning of the nozzles of the print head is effected by means of a body which is impregnated with the cleaning liquid and is periodically passed over the print head in the region of the nozzles at a contact pressure. from 0.01 to 1 N / mm2, preferably from 0.02 to 0.05 N / mm2, Process according to at least one of the preceding claims, characterized in that the cleaning of the printhead nozzles is conducted under ultrasound action. Method according to Claim 28, characterized in that the cleaning of the print head nozzles is periodically conducted under ultrasound action between the print cycles on the print cartridge or the print head. Process according to at least one of the preceding claims, characterized in that the printed layers are dried at a temperature of 65 to 105 ° C. Process according to Claim 30, characterized in that each individual layer is dried after printing. Process according to Claim 31, characterized in that each individual layer is printed in the printing region of the heat-detecting jet printer to a temperature in the range of 65 to 105 ° C, preferably 68 ° C to 85 ° C if using a fan, applying reduced pressure or convection flow to remove doliquid vapor. Process according to Claim 32, characterized in that the heating is effected by radiation with a halogen lamp, an infrared lamp, ionic radiation, laser radiation or by using heating elements located in the printing region. Process according to at least one of the preceding claims, characterized in that the individual printed layers of ceramic material have a thickness of 1 μπι to 30 μm, preferably 0.05 μm to 10 μm, after drying of the individual printed layers of the vaporising material. during the hardening of the layered composite it has a thickness of 0.05 μm to 5 μm. Process according to at least one of the preceding claims, characterized in that the hardening of the dry-layer composite is appropriate after storage at about 80 ° C in a drying oven by sintering the ceramic material. Process according to Claim 35, characterized in that the sintering is conducted at a temperature of 800 ° C to 1500 ° C. Process according to claim 35 or 36, characterized in that the sintering is conducted at a sintered density of 100% of the theoretical density, preferably up to 98% of this density. 38. A method according to at least one of the preceding claims, characterized in that medical ceramic prostheses, in particular body, limbs and head, head, face, oral cavity, dental implants, dental fillings, dental crowns and dental bridges are produced as ceramic bodies. three-dimensional.